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diff --git a/share/man/man4/tmpfs.4 b/share/man/man4/tmpfs.4 new file mode 100644 index 000000000000..7d24f7db9aea --- /dev/null +++ b/share/man/man4/tmpfs.4 @@ -0,0 +1,229 @@ +.\"- +.\" Copyright (c) 2007 Xin LI +.\" Copyright (c) 2017 The FreeBSD Foundation +.\" +.\" Part of this documentation was written by +.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship +.\" from the FreeBSD Foundation. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS DOCUMENTATION IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR +.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES +.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. +.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, +.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT +.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF +.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +.\" +.\"- +.\" Copyright (c) 2005, 2006 The NetBSD Foundation, Inc. +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS +.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED +.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR +.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS +.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR +.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF +.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS +.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN +.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) +.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +.\" POSSIBILITY OF SUCH DAMAGE. +.\" +.Dd September 18, 2023 +.Dt TMPFS 4 +.Os +.Sh NAME +.Nm tmpfs +.Nd "in-memory file system" +.Sh SYNOPSIS +To compile this driver into the kernel, +place the following line in your +kernel configuration file: +.Bd -ragged -offset indent +.Cd "options TMPFS" +.Ed +.Pp +Alternatively, to load the driver as a +module at boot time, place the following line in +.Xr loader.conf 5 : +.Bd -literal -offset indent +tmpfs_load="YES" +.Ed +.Sh DESCRIPTION +The +.Nm +driver implements an in-memory, or +.Nm +file system. +The filesystem stores both file metadata and data in main memory. +This allows very fast and low latency accesses to the data. +The data is volatile. +An umount or system reboot invalidates it. +These properties make the filesystem's mounts suitable for fast +scratch storage, like +.Pa /tmp . +.Pp +If the system becomes low on memory and swap is configured +.Po see +.Xr swapon 8 Pc , +the system can transfer file data to swap space, freeing memory +for other needs. +Metadata, including the directory content, is never swapped out by the +current implementation. +Keep this in mind when planning the mount limits, especially when expecting +to place many small files on a tmpfs mount. +.Pp +When +.Xr mmap 2 +is used on a file from a tmpfs mount, the swap VM object managing the +file pages is used to implement mapping and avoid double-copying of +the file data. +This quirk causes process inspection tools, like +.Xr procstat 1 , +to report anonymous memory mappings instead of file mappings. +.Sh OPTIONS +The following options are available when +mounting +.Nm +file systems: +.Bl -tag -width "maxfilesize" +.It Cm easize +Set the maximum memory size used by extended attributes in bytes. +The default is 16 megabytes. +.It Cm export +Accept the +.Cm export +option for compatibility with +.Xr nfsv4 4 . +This option does nothing. +.It Cm gid +Set the group ID of the root inode of the file system. +The default is the mount point's GID. +.It Cm inodes +Set the maximum number of nodes available to the file system. +If not specified, the file system chooses a reasonable maximum based on +the file system size, which can be limited with the +.Cm size +option. +.It Cm maxfilesize +Set the maximum file size in bytes. +The default is the maximum possible value. +.It Cm mode +Set the mode (in octal notation) of the root inode of the file system. +The default is the mount point's mode. +.It Cm nomtime +Disable the tracking of mtime updates caused by writes to the +shared mapped areas backed by +.Nm +files. +This option removes periodic scans, +which downgrade read-write-mapped pages to read-only to note the writes. +.It Cm nonc +Do not use namecache to resolve names to files for the created mount. +This saves memory, but currently might impair scalability for highly +used mounts on large machines. +.It Cm nosymfollow +Do not follow +.Xr symlink 7 Ap s +on the mounted file system. +.It Cm pgread +Enable pgcache read for the mount. +.It Cm size +Set the total file system size in bytes, unless suffixed +with one of k, m, g, t, or p, which denote byte, kilobyte, +megabyte, gigabyte, terabyte and petabyte respectively. +If zero (the default) or a value larger than SIZE_MAX - PAGE_SIZE +is given, the available amount of memory (including +main memory and swap space) will be used. +.It Cm uid +Set the user ID of the root inode of the file system. +The default is the mount point's UID. +.It Cm union +Refer to +.Xr mount 8 . +.El +.Sh SYSCTL VARIABLES +The following +.Xr sysctl 8 +variables are available: +.Bl -tag -width indent +.It Va vfs.tmpfs.memory_percent +The percentage of memory plus swap space available at kernel file system +initialization that can be used by a file system with a size of 0. +When this amount of space in use is reached, new files cannot be created +and files cannot be extended. +The default is 95%. +Changing this value also changes +.Va vfs.tmpfs.memory_reserved . +.It Va vfs.tmpfs.memory_reserved +The currently-reserved amount of memory plus swap space +based on the memory percentage. +The minimum is compiled into the system, and defaults to 4 MB. +.El +.Sh EXAMPLES +Mount a +.Nm +memory file system: +.Pp +.Dl "mount -t tmpfs tmpfs /tmp" +.Pp +Configure a +.Nm +mount via +.Xr fstab 5 : +.Bd -literal -offset indent +tmpfs /tmp tmpfs rw 0 0 +.Ed +.Sh SEE ALSO +.Xr procstat 1 , +.Xr mmap 2 , +.Xr nmount 2 , +.Xr unmount 2 , +.Xr fstab 5 , +.Xr mdmfs 8 , +.Xr mount 8 , +.Xr swapinfo 8 , +.Xr swapon 8 +.Sh HISTORY +The +.Nm +driver first appeared in +.Fx 7.0 . +.Sh AUTHORS +.An -nosplit +The +.Nm +kernel implementation was written by +.An Julio M. Merino Vidal Aq Mt jmmv@NetBSD.org +as a Google Summer of Code project. +.Pp +.An Rohit Jalan +and others ported it from +.Nx +to +.Fx . +.Pp +This manual page was written by +.An Xin LI Aq Mt delphij@FreeBSD.org . |